Control of exhaust energy in internal combustion engines

Abstract

Methods of improving SCR performance in heavy duty vehicles may use multiple interdependent control techniques to increase engine exhaust temperatures in a fuel efficient manner. One method combines cylinder deactivation and mechanical loading of an engine by an electrical generator used to input energy into an exhaust stream to manipulate the exhaust temperature through the combined effect of modified air-to-fuel ratio and supplemental energy input. In particular, cylinder deactivation may be used to modify the engine air flowrate and the electric generator may be used to apply mechanical load on the engine to manipulate the engine fuel flow rate to control the engine air-to-fuel ratio and thereby increase exhaust temperatures. The exhaust temperatures may be further increased by using the electrical generator to add the energy generated as input energy to the exhaust stream.

The invention claimed is: 
     
       1. A method, comprising:
 idling an internal combustion engine, thereby producing exhaust; 
 reducing a speed at which firing cylinders of the internal combustion engine run, thereby reducing a volumetric flow rate of air through the engine; 
 increasing a mechanical load to the engine, thereby increasing an amount of fuel demanded by the engine; and 
 inputting energy from a source of electrical energy into the exhaust. 
 
     
     
       2. The method of  claim 1 , wherein increasing a mechanical load to the engine includes using the running engine to drive an electric generator. 
     
     
       3. The method of  claim 2 , further comprising charging a store of energy with energy generated by the electric generator. 
     
     
       4. The method of  claim 2  wherein the electric generator is the source of electric energy. 
     
     
       5. The method of  claim 1  wherein inputting energy into the exhaust includes using an electrically heated catalyst system. 
     
     
       6. The method of  claim 1  wherein reducing the volumetric flow rate of air through the engine includes reducing the volumetric flow rate of air through the engine by half. 
     
     
       7. The method of  claim 1 , further comprising deactivating one or more cylinders of the engine. 
     
     
       8. The method of  claim 1 , further comprising recirculating the exhaust through the engine. 
     
     
       9. The method of  claim 1  wherein reducing a speed at which firing cylinders of the internal combustion engine run is performed simultaneously with increasing a mechanical load to the engine and inputting energy into the exhaust. 
     
     
       10. The method of  claim 1  wherein reducing a speed at which firing cylinders of the internal combustion engine run is performed concurrently with increasing a mechanical load to the engine and inputting energy into the exhaust. 
     
     
       11. A heavy duty vehicle, comprising:
 an internal combustion engine; 
 an exhaust after-treatment system; and 
 a control system; 
 wherein the control system, in operation, controls the vehicle, the internal combustion engine, and the exhaust after-treatment system to: 
 idle the internal combustion engine; 
 reduce a speed at which firing cylinders of the internal combustion engine run; 
 use the internal combustion engine to drive an electric generator; and 
 input electrical energy generated by the electric generator into exhaust produced by the internal combustion engine. 
 
     
     
       12. The vehicle of  claim 11  wherein the internal combustion engine is a diesel engine. 
     
     
       13. The vehicle of  claim 11  wherein the exhaust after-treatment system includes a diesel oxidation catalyst. 
     
     
       14. The vehicle of  claim 11  wherein the exhaust after-treatment system includes a diesel particulate filter. 
     
     
       15. The vehicle of  claim 11  wherein the exhaust after-treatment system includes a selective catalytic reduction system. 
     
     
       16. The vehicle of  claim 11  wherein the exhaust after-treatment system includes an ammonia oxidation catalyst system.